L5980 STMicroelectronics, L5980 Datasheet
L5980
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L5980 Summary of contents
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... Figure 1. Application circuit November 2009 0.7 A step-down switching regulator VFQFPN8 Description The L5980 is step-down switching regulator with 1 A (min.) current limited embedded power MOSFET able to deliver in excess of 0 current to the load depending on the application condition. The input voltage can range from 2 while the output voltage can be set starting from 0 ...
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... Output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.4 Compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.4.1 5.4.2 5.5 Thermal considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 5.6 Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 5.7 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 6 Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 6.1 Positive buck-boost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 6.2 Inverting buck-boost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 2/42 Type III compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Type II compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Doc ID 13003 Rev 6 L5980 ...
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... L5980 8 Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Doc ID 13003 Rev 6 Contents 3/42 ...
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... Vout to FB pin. The switching frequency can be increased connecting an external resistor from FSW pin and ground. If this pin is left floating the device works at its free-running frequency of 250 kHz. Ground Unregulated DC input voltage CC Doc ID 13003 Rev GND GND FSW FSW FB FB Description L5980 ...
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... L5980 2 Maximum ratings 2.1 Absolute maximum ratings Table 2. Absolute maximum ratings Symbol Vcc OUT F , COMP, SYNCH Analog pin SW INH FB P TOT stg 2.2 Thermal data Table 3. Thermal data Symbol R thJA 1. Package mounted on demonstration board. Parameter Input voltage Output DC voltage Inhibit pin ...
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... Values Min Typ Max 2.9 18 2.9 0.175 0.3 140 170 140 220 1.0 1.3 1.6 225 250 275 220 275 1.254 0 100 1000 (1) 0.593 0.6 0.607 2 0.6 1.9 7.5 10 7.4 8.2 9.1 2 L5980 Unit V mΩ A kHz V % kHz V mA μA V μA ms ...
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... L5980 Table 4. Electrical characteristics (continued) Symbol V High level output voltage CH V Low level output voltage CL I Bias source current FB I Source COMP pin O SOURCE I Sink COMP pin O SINK G Open loop voltage gain V Synchronization function High input voltage Low input voltage Slave sink current ...
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... Functional description 4 Functional description The L5980 is based on a “voltage mode”, constant frequency control. The output voltage V is sensed by the feedback pin (FB) compared to an internal reference (0.6 V) providing OUT an error signal that, compared to a fixed frequency sawtooth, controls the on and off time of the power switch ...
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... L5980 4.1 Oscillator and synchronization Figure 4 shows the block diagram of the oscillator circuit. The internal oscillator provides a constant frequency clock. Its frequency depends on the resistor externally connect to FSW pin. In case the FSW pin is left floating the frequency is 250 kHz; it can be increased as ...
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... Functional description Figure 5. Sawtooth: voltage and frequency feed forward; external synchronization Figure 6. Oscillator frequency versus FSW pin resistor 10/42 Doc ID 13003 Rev 6 L5980 ...
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... L5980 4.2 Soft-start The soft-start is essential to assure correct and safe start up of the step-down converter. It avoids inrush current surge and makes the output voltage increases monothonically. The soft-start is performed by a staircase ramp on the non-inverting input (V amplifier. So the output voltage slew rate is: ...
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... III compensation network has to be used (see compensation network selection). Anyway the methodology to compensate the loop is to introduce zeros to obtain a safe phase margin. 12/42 GBWP Slew rate Chapter 5.4 Doc ID 13003 Rev 6 L5980 Value 100 dB 4.5 MHz 7 V/μ 3 mA/40 mA for details about the ...
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... L5980 4.4 Overcurrent protection The L5980 implements the overcurrent protection sensing current flowing through the power MOSFET. Due to the noise created by the switching activity of the power MOSFET, the current sensing is disabled during the initial phase of the conduction time. This avoids an erroneous detection of a fault condition. This interval is generally known as “masking time” ...
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... The thermal shutdown block generates a signal that turns off the power stage if the junction temperature goes above 150 °C. Once the junction temperature goes back to about 130 °C, the device restarts in normal operation. The sensing element is very close to the PDMOS area, so ensuring an accurate and fast temperature detection. 14/42 Doc ID 13003 Rev 6 L5980 ...
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... L5980 5 Application information 5.1 Input capacitor selection The capacitor connected to the input has to be capable to support the maximum input operating voltage and the maximum RMS input current required by the device. The input capacitor is subject to a pulsed current, the RMS value of which is dissipated over its ESR, affecting the overall system efficiency ...
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... T = OFF L is the conduction OFF + T )).The maximum current ripple, at OFF 1 D – F MIN ⋅ ---------------------- - OFF = 250 kHz the minimum SW Δ ------- - 2 Inductor value (μH) Saturation current ( 1. 1. 1 1. 1. 1. 1.9 to 2.7 L5980 ...
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... L5980 5.3 Output capacitor selection The current in the capacitor has a triangular waveform which generates a voltage ripple across it. This ripple is due to the capacitive component (charge and discharge of the output capacitor) and the resistive component (due to the voltage drop across its ESR). So the output capacitor has to be selected in order to have a voltage ripple compliant with the application requirements ...
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... Compensation network The compensation network has to assure stability and good dynamic performance. The loop of the L5980 is based on the voltage mode control. The error amplifier is a voltage operational amplifier with high bandwidth. So selecting the compensation network the E/A will be considered as ideal, that is, its bandwidth is much larger than the system one. ...
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... L5980 Equation 13 where: Equation 14 Equation 15 As seen in Chapter 4.3 following paragraph the guidelines to select the type II and type III compensation network are illustrated. 5.4.1 Type III compensation network The methodology to stabilize the loop consists of placing two zeros to compensate the effect of the LC double pole, so increasing phase margin; then to place one pole in the origin to minimize the dc error on regulated output voltage ...
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... Choose a value for R 2. Choose a gain (R 20/ ----------------------------- - ⋅ ⋅ 2π ( · G (f) · G LOOP PW0 LC , usually between 1 kΩ and 5 kΩ order to have the required bandwidth (BW), that means Doc ID 13003 Rev ------------------------------------------- - ⋅ ⋅ ⋅ ------------------- - 2π · G PW0 (f)) are drawn. TYPEIII L5980 (f)) LC ...
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... L5980 Equation 18 where K is the feed forward constant and 1/K is equals Calculate C 4 Equation 19 4. Calculate C 5 Equation 20 5. Set also the first pole at four times the system bandwidth and also the second zero at the output filter double pole: Equation 21 The suggested maximum system bandwidth is equals to the switching frequency divided by 3 ...
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... Application information Figure 12. Open loop gain Bode diagram with ceramic output capacitor 22/42 Doc ID 13003 Rev 6 L5980 ...
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... L5980 5.4.2 Type II compensation network If the equivalent series resistance (ESR) of the output capacitor introduces a zero with a frequency lower than the desired bandwidth (that is: 2π * ESR * C helps stabilize the loop. Electrolytic capacitors show not negligible ESR (>30 mΩ), so with this kind of output capacitor the type II network combined with the zero of the ESR allows stabilizing the loop ...
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... R = ⎝ ⎠ ESR f = ------------------------------------------- - ⋅ ESR 2π ESR C by placing the zero one decade below the output filter double pole ------------------------------ - 4 ⋅ 2π order to place the second pole at four times the system bandwidth 3 Doc ID 13003 Rev ⋅ ⋅ -------- - ⋅ OUT ⋅ L5980 ...
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... L5980 Equation 25 For example with V ESR = 50 mΩ, the type II compensation network is: In Figure 15 is shown the module and phase of the open loop gain. The bandwidth is about 35 kHz and the phase margin is 49° ------------------------------------------------------------- - ⋅ ⋅ 5 2π 0 μ 1 OUT 1.1kΩ ...
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... Application information Figure 15. Open loop gain Bode diagram with electrolytic/tantalum output capacitor 26/42 Doc ID 13003 Rev 6 L5980 ...
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... L5980 5.5 Thermal considerations The thermal design is important to prevent the thermal shutdown of device if junction temperature goes above 150 °C. The three different sources of losses within the device are: a) conduction losses due to the not negligible R equal to: Equation 26 Where D is the duty cycle of the application and the maximum R the duty cycle is theoretically given by the ratio between V higher to compensate the losses of the regulator ...
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... Thanks to the exposed pad of the device, the ground plane helps to reduce the thermal resistance junction to ambient large ground plane enhances the thermal performance of the converter allowing high power conversion. In Figure 17 a layout example is shown. 28/42 measured on the demonstration board described in the following Doc ID 13003 Rev 6 L5980 ...
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... L5980 Figure 17. Layout example Doc ID 13003 Rev 6 Application information 29/42 ...
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... A Doc ID 13003 Rev 6 L1 15uH L1 15uH Vout=3.3V Vout=3.3V Vout=3.3V Vout=3. STPS2L25U STPS2L25U STPS2L25U STPS2L25U R1 4.99K R1 4.99K R1 4.99K R1 4.99K R3 180 R3 180 C3 3.3nF C3 3.3nF R2 1.1K R2 1.1K R2 1.1K R2 1.1K Description Manufacturer MURATA MURATA STMicroelectronics Wurth elektronik L5980 22uF 22uF 22uF 22uF ...
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... L5980 Figure 19. PCB layout (component side) Figure 20. PCB layout (bottom side) Figure 21. PCB layout (front side) Doc ID 13003 Rev 6 Application information 31/42 ...
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... Figure 27. Efficiency vs output current 95 90 Vo=3.3V 85 Vo=2.5V 80 Vo=1. 0.1 0.5 0.6 0.7 Doc ID 13003 Rev 6 current Vo=5.0V Vo=3.3 Vo=2.5V VCC=12V F =250KHz SW 0.2 0.3 0.4 0.5 0.6 Io [A] Vo=2.5V Vo=1.8V Vo=1.2V VCC=3.3V F =250KHz SW 0.2 0.3 0.4 0.5 0.6 Io [A] L5980 0.7 0.7 ...
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... L5980 Figure 28. Load regulation 0.14 F =250KHz SW 0.12 0.1 0.08 0.06 0.04 0.02 0 0.1 0.2 0.3 0.4 Io [A] Figure 30. Short circuit behavior OUT OUT OUT OUT OUT OUT OUT 10V/div 10V/div 10V/div 10V/div 10V/div 10V/div 10V/div OUTPUT OUTPUT OUTPUT OUTPUT OUTPUT OUTPUT ...
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... Application ideas 6.1 Positive buck-boost The L5980 can implement the step up/down converter with a positive output voltage. Figure 33 shows the schematic: one power MOSFET and one Schottky diode are added to the standard buck topology to provide 12 V output voltage with input voltage from 2 ...
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... L5980 Equation 32 where I is the average current in the embedded power MOSFET in the ON time chose the right value of the inductor and to manage transient output current, that for short time can exceed the maximum output current calculated by current in the power MOSFET has to be calculated. The peak current, showed in 33, must be lower than the minimum current limit (1 ...
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... V D power MOSFET. 6.2 Inverting buck-boost The L5980 can implement the step up/down converter with a negative output voltage. Figure 33 shows the schematic to regulate - further external components are added to the standard buck topology. The relationship between input and output voltage is: ...
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... L5980 As in the positive one, in the inverting buck-boost the current flowing through the power MOSFET is transferred to the load only during the OFF time. So according to the maximum DC switch current (0.7 A), the maximum output current can be calculated from the 32, where the duty cycle is given by Figure 35 ...
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... Package mechanical data 7 Package mechanical data In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: ECOPACK® trademark. 38/42 Doc ID 13003 Rev 6 L5980 www.st.com. ...
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... L5980 Table 10. VFQFPN8 ( 1.08 mm) mechanical data Dim ddd Figure 37. Package dimensions mm Min Typ Max 0.80 0.90 1.00 0.02 0.05 0.70 0.20 0.18 0.23 0.30 2.95 3.00 3.05 2.23 2.38 2.48 2.95 3.00 3.05 1.49 1.64 1.74 0.50 0.30 0.40 0.50 0.08 ...
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... Order codes 8 Order codes Table 11. Order codes Order codes L5980 L5980TR 40/42 Package VFQFPN8 ( 1.08 mm) Doc ID 13003 Rev 6 L5980 Packaging Tube Tube and reel ...
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... L5980 9 Revision history Table 12. Document revision history Date 21-Dec-2006 18-Oct-2007 09-Sep-2008 27-Jan-2009 15-Jun-2009 16-Nov-2009 Revision 1 Initial release 2 Document status promoted from preliminary data to datasheet Updated: Cover page, Figure 9 on page 18, 3 Table 4 on page 6, Table 8 on page Added: Table 3 on page 5 ...
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... Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan - Malaysia - Malta - Morocco - Philippines - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States of America 42/42 Please Read Carefully: © 2009 STMicroelectronics - All rights reserved STMicroelectronics group of companies www.st.com Doc ID 13003 Rev 6 L5980 ...